Field
This disclosure is generally related to the design of photovoltaic (or “PV”) modules. More specifically, this disclosure is related to the design and manufacture of colored photovoltaic roof tiles.
Related Art
Commercial solar panels are constructed from arrays of photovoltaic (or “PV”) modules. Each PV module, in turn, typically includes a two-dimensional array (e.g., 6×12) of solar cells. Usually, the color appearance of these modules is the natural color of the solar cells embedded in the PV modules, which can be blue, dark-blue, or black. But customers often wish to choose the color appearance of PV modules so that, for example, the modules match the color of the buildings in which they are integrated.
Several existing techniques are available to provide color to PV modules. One technique involves applying tinted glass and/or colored encapsulation sheets. However, these extra structures can absorb a large amount of sunlight, causing significant PV power loss. Moreover, these structures' color appearance may degrade over time.
Another coloration technique involves applying a film over the PV modules or solar cells. However, the color appearance achieved by the coatings on conventional glass typically suffers from flop, or angle-sensitivity, and can also degrade over time under environmental stresses (such as marine weather).
Shading, or absorption of incident sunlight, causes PV power loss, a consequential problem of existing coloring techniques. In addition, colored PV modules manufactured with these techniques, and colored glass more generally, commonly suffer from: sparkle, or glint; flop, or angle-dependent color appearance; and graininess. Note that sparkle refers to glint or localized bright spots. Flop, on the other hand, usually refers to angle-dependent color, i.e. an angular dependence of the peak reflected wavelength. The term flop, or light-dark flop, can also refer to angle-dependent brightness, i.e. an angular dependence of total reflectivity.